The present invention relates to connecting electrical wires with twist-on type connectors; and more particularly, to tools for fastening such connectors.
The ends of two or more wires of an electrical circuit are often connected together using a twist-on type wire connector. These connectors are available in a variety of sizes and shapes and commonly have a conical shaped body of insulating material, such as plastic, with an opening at the larger end. The opening communicates with a tapered aperture which has helical threads cut in the interior surface of the body. The fastening operation is performed by inserting the stripped ends of two or more wires into the open end and rotating the connector so that the threads screw onto and twist the wires together to form an electrical coupling. An improved connector has a tapered metal spring inserted into the aperture of the insulating body. The spring engages the bare wires and aids in providing a conductive path there between.
Twist-on type wire connectors frequently are used by electricians to connect two or more wires in a junction box within a building. In this application, electricians typically twist on the connectors by hand, although manual tools, such as a hexagonal socket wrench or a nut driver, can be used. These connectors also are employed in a variety of electrical appliances. For example, connections between the wires of a ballast in a fluorescent lighting fixture and the electrical supply cord are made in this manner. In a factory, the wire connectors often are attached using a pneumatically or electrically powered nut driver because of the high volume assembly at a fixed location. These power tools have a socket specifically designed to engage the body of the connector.
A fastening tool, especially an power-driven one, easily can apply an excessive amount of torque to the connector, thus damaging either the wires or the connector. If cracks in the connector are undetected, a short circuit could occur at the connection.
One solution to this problem was to limit the torque with a clutch mechanism between the tool motor and the socket. However, torque limiting devices add additional expense, size and weight to the tool, and require adjustment to the optimum level for each specific wiring application.